Method and arrangement for transporting and inspecting semiconductor substrates

ABSTRACT

The invention relates to an arrangement for transporting and inspecting semiconductor substrates ( 6 ), having at least three workstations ( 8, 10, 12 ), a changer ( 14 ), which has at least three arms ( 14   a   , 14   b   , 14   c ) which are designed to load the individual workstations ( 8, 10, 12 ) with semiconductor substrates ( 6 ). A measuring device ( 15 ) is assigned to the second workstation ( 10 ), determines the deviation of the current position of the semiconductor substrate ( 6 ) and makes it available to the arrangement ( 3 ) for the further inspection of the semiconductor substrate ( 6 ). In addition, the changer ( 14 ) is not equipped with means for exact positioning of the semiconductor substrates ( 6 ) in the workstations ( 8, 10, 12 ).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.10/379,677, filed Mar. 6, 2003, now U.S. Pat. No. 6,789,436, which is adivisional of U.S. application Ser. No. 10/053,628, filed Jan. 24, 2002,now U.S. Pat. No. 6,553,850, the entire contents of which areincorporated herein by reference.

This invention claims priority of the German patent application 101 03253.6 which is incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a method for transporting and inspectingsemiconductor substrates. In addition, the invention relates to anarrangement for transporting and inspecting semiconductor substrates.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 5,863,170 discloses a modular process system forsemiconductors. This system, for handling wafers, is of modularconstruction and has a large number of process stations, which areloaded with wafers. The wafers are forwarded from process station toprocess station by a central carousel. In the process stations, variousprocess steps are carried out on the wafers. This arrangement can beused only for treatment in various process stations. Monitoring andinspection of the wafers is not provided.

U.S. Pat. No. 5,807,062 discloses an arrangement for handling wafer-likeobjects. The wafers in the arrangement are transferred from and tomagazines. In the arrangement itself there are arranged threeworkstations. In the first workstation, the wafer-like object is alignedwith respect to a plane and an angle. The next workstation representsthe x/y table of an inspection microscope. The third workstation is usedfor the visual monitoring of the wafer-like objects by an operator. Theworkstations are in each case arranged at an angle of 120° to oneanother. A changer sits between the workstations and, with its threearms, can feed the wafer-like objects to the individual workstations.The changer has three arms and additional means for the fine positioningof the wafer-like objects.To this end, there is on the shaft of the changer a gearwheel, in whichjaws with identical toothing engage and thus permit fine adjustment ofthe changer. The drawback with this arrangement is that it cannot beused so universally, and fine positioning takes up a relatively longtime.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a method with whichwafer-like objects can be handled in a time-saving manner, and a highthroughput of the wafer-like objects is achievable with this method.

The object is achieved by a method comprising the steps of:

-   -   providing at least three workstations arranged in a housing,        wherein a changer being arranged in such a way that each of the        workstations can be supplied with a semiconductor substrate;    -   lifting the changer and carrying out a rotational movement by a        specific angular amount, in order to transfer al least one of        the semiconductor substrates to another workstation;    -   lowering the changer and carrying out a rotational movement by        the same angular amount in the opposite direction, without a        semiconductor substrate resting on the changer; and    -   picking up a new semiconductor substrate from a substrate feed        module.        It is a further object of the invention to provide an        arrangement which permits wafer-like objects to be inspected        visually and microscopically in a simple, timesaving manner.        Added to this is the intention that the arrangement shall also        be able to operate with inaccurately positioned wafer-like        objects. Furthermore, wafer-like objects of different sizes are        intended also to be processed with the invention.        The object is achieved by an arrangement for transporting and        inspecting semiconductor substrates which comprises at least        three workstations, a changer defining an axis of rotation,        wherein the changer has at least three arms, and which is        designed to load the at least three workstations with        semiconductor substrates, the workstations being arranged        coaxially around the axis of rotation of the changer, a        measuring device is assigned to one workstation, wherein the        measuring device determines the deviation of the current        position of the semiconductor substrate from an intended        position and makes it available to the arrangement for the        further inspection of the semiconductor substrate and in that        the changer is not equipped with means for moving the        semiconductor substrates into the intended position.        It is advantageous to have an arrangement for transporting and        inspecting semiconductor substrates. The arrangement comprises:    -   a first, second and third workstation,    -   a changer defining an axis of rotation, wherein the changer has        three arms, and which is designed to load and unload the three        workstations with semiconductor substrates,    -   the first workstation defines a transfer position, at which        semiconductor substrates are introduced into the arrangement        from a substrate feed module and can be transferred from the        arrangement to the substrate feed module,    -   the second workstation is a measuring device, which determines        the deviation of the current position of the semiconductor        substrate from an intended position and makes it available to        the arrangement for the further inspection of the semiconductor        substrate, and    -   the third workstation defines a micro inspection and comprises        an x/y table, which feeds the semiconductor substrate to a        microscope.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject of the invention is illustrated schematically in the drawingand will be described below using the figures, in which:

FIG. 1: shows a schematic view of the arrangement, which is connected toa substrate feed module for wafer-like objects;

FIG. 2: shows a further exemplary embodiment of a possible set-up of thearrangement and of the substrate feed module;

FIG. 3: shows a schematic illustration of the configuration of theworkstation in side view in the area of the optical inspectionmicroscope;

FIG. 4: shows a plan view of the arrangement to clarify the flow of thesemiconductor substrates;

FIG. 5: shows an illustration of two cycles in a possible scenario ofthe flow of the semiconductor substrates in the arrangement, macroinspection by the user being dispensed with;

FIG. 6: shows an illustration of two cycles in a further scenario of theflow of the semiconductor substrates in the arrangement, a macroinspection additionally being carried out;

FIG. 7: shows an illustration of a cycle in which a poor semiconductorsubstrate has been found during the visual macro inspection; and

FIG. 8: shows an illustration of the handling of semiconductorsubstrates, in which only one semiconductor substrate per cycle isinspected in the arrangement, and no visual macro inspection is carriedout.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows, in schematic form, a lateral assignment of a substratefeed module 1 to an arrangement 3 having a plurality of workstations 8,10, 12. The substrate feed module 1 in this exemplary embodiment isoriented with respect to the arrangement 3 in such a way that it can beloaded with substrates from its front side 2 via one or more load ports2 a, 2 b. Normally, two load ports 2 a, 2 b are provided. In this case,open or closed cassettes 4 are used, which are inserted manually, by theuser, or by means of automation, for example by means of a robot, intothe load ports 2 a, 2 b. The cassettes 4 can be filled withsemiconductor substrates 6 or can also be empty, depending on theworking sequence envisaged. For example, all the cassettes 4 can befilled and semiconductor substrates 6 are first removed from onecassette 4, inserted into the arrangement 3 and, after treatment andmonitoring there, are put back into the same cassette 4 again. Thisprocedure is then repeated for the next cassette 4, while the userretrieves the cassette 4 with the processed semiconductor substrates 6and, in its place, inserts a new cassette 4 with semiconductorsubstrates 6 into the free load port 2 a, 2 b. Provided in the interiorof the substrate feed module 1 is a transport robot 5, which transfersthe semiconductor substrates 6 into the arrangement 3. The arrangementof the substrate feed module 1 in FIG. 1 is merely one of a plurality ofpossible configurations. Likewise, the substrate feed module 1 can berotated through 90°, so that the cassettes point away from thearrangement 3.

As already mentioned, a plurality of workstations 8, 10 and 12 areprovided in the arrangement 3. At the workstations 8, 10 and 12,appropriate investigations, monitoring and inspections are carried outon the semiconductor substrates 6. In the present exemplary embodiment,three workstations, a first, a second and a third workstation 8, 10 and12, are provided in the arrangement.

Arranged centrally between the workstations 8, 10 and 12 is a changer 14for the semiconductor substrates 6. The changer 14 has three arms 14 a,14 b and 14 c, with which the individual workstations 8, 10 and 12 canbe supplied simultaneously with the semiconductor substrates 6. Thefirst workstation 8 is used for acceptance from and transfer to thesubstrate feed module 1. The second workstation 10 is used for thealignment, for the determination of the positioning and for the visualinspection of the semiconductor substrates 6. In order to align thesemiconductor substrates 6, the second workstation 10 is assigned ameasuring device 15, which detects marks applied to the semiconductorsubstrate 6 and determines codings on the semiconductor substrates.Furthermore, the measuring device 15 determines the deviation from theaccurately-positioned deposition of the semi-conductor substrate 6 inthe second workstation 10. The data determined in this way are forwardedto a central processing unit (not shown). The third workstation 12 isdesigned for the micro inspection of the semiconductor substrates 6. Thethird workstation 12 has an x/y table 17, which feeds the semiconductorsubstrate 6 to a microscope 16 for the micro inspection. A zdisplacement can also be made possible by the x/y table. The arrangement3 is surrounded by a housing 18, which shuts off the three workstations8, 10 and 12 and the microscope 16 with respect to the ambient air andprovides the correspondingly required clean-room conditions. Added tothis is the fact that the possibility of intervention by the user in thearrangement 3 is likewise prevented by the housing 18, whichadditionally constitutes a security aspect. In the embodiment disclosedhere, the microscope 16 is provided with an eyepiece 20, which providesthe user with the possibility of carrying out a visual micro inspectionof the semiconductor substrates 6 to be examined. Of course, thesemiconductor substrates 6 can be inspected automatically by themicroscope 16 in the third workstation 12. The housing 18 of thearrangement 3 and the substrate feed module 1 have docking elements 22,which permit a variable association between substrate feed module 1 andarrangement 3.An exemplary embodiment of the this variable association is shown inFIG. 2 and shows a possible setup of the arrangement 3 and the substratefeed module 1. The arrangement 3 defines a transfer position 24, atwhich the semiconductor substrates 6 are introduced into the arrangement3 by the substrate feed module 1. For this purpose, the docking elements22 are fitted in or on the housing 18 of the arrangement 3 in anappropriate way. From the cassettes 4, the semiconductor substrates 6pass via the load ports 2 a, 2 b into the substrate feed module 1 and,from there by means of the transport robot 5, to the transfer position24 of the arrangement 3.FIG. 3 shows a schematic illustration of the configuration of theworkstation in side view in the area of the optical inspectionmicroscope 16. The changer 14 can be rotated freely about an axis ofrotation 13. In addition, the changer 14 can be moved up and downaxially, in order in this way to pick up the semiconductor substrates 6or set them down in the third workstation 12. The axial movement of thechanger 14, which likewise corresponds to the movement in the zdirection, is represented by a double arrow A-A. In the lifted position14 up, the changer 14 is shown dashed. In the lifted position 14 up ofthe changer 14, the changer is able to move with its arms above a plane19 which is defined by a wafer set down in the workstation 12. The plane19 is illustrated in FIG. 3 by a thick dashed line. In addition, theworkstation 12 has a cutout 21, through which the changer 14 can freelyrotate its arms 14 a and 14 b. The cutout 21 makes it possible for thechanger 14 to rotate freely in the forward and reverse directions whenin the lowered position. The second workstation 10, in the basicposition in FIG. 3, is likewise represented by continuous lines. Thesecond workstation 10 can be moved into a central position 10 m and intoa lifted position 10 up. In the central position 10 m, the secondworkstation 10 is at the level of the plane 19. As already mentioned inFIG. 1, the second and third workstations 10 and 12 are arrangedphysically in such a way that they can be supplied with semiconductorsubstrates 6 by the arms 14 a and 14 b of the changer 14.FIG. 4 shows a schematic plan view of the arrangement 3 to clarify theflow of the semiconductor substrates 6. An arrow 26 in FIG. 4 marks thepoint at which the semiconductor substrates 6 are introduced into thearrangement 3. In a preferred embodiment, the changer 14 has three arms14 a, 14 b and 14 c, which are each arranged at an angle of 120°. Thechanger 14 guides the semiconductor substrates 6 to the individualworkstations 8, 10 and 12. The first workstation 8 is the transferposition 8 a, the second workstation 10 is the macro inspection 10 a,and the third workstation 12 is the micro inspection 12 a. The transferposition 8 a, macro inspection 10 a and micro inspection 12 a define theposition of the changer 14 at which the semiconductor substrates 6 areaccepted by the workstations 8, 10 and 12 or are transferred to theworkstations 8, 10 and 12. Given optimum utilization, there are threesemiconductor substrates in the arrangement 3 at the same time,simultaneous macro inspection 10 a and micro inspection 12 a beingpossible. The dashed circle in FIG. 4 defines an outer movement circle28 of the changer 14 together with the semiconductor substrates 6resting on the changer 14. Each of the semiconductor substrates 6 has anidentification 30 and a notch 32. The identification 30 comprises, forexample, a barcode, a numeric identification, an alphanumericidentification or combinations thereof. The notch 32 is used todetermine the orientation of the semiconductor substrate 6 and,consequently, also for its precise spatial alignment.FIG. 5 shows a graphical representation of two cycles n and n+1 in apossible scenario of the flow of the semiconductor substrates 6 in thearrangement 3. The time t is plotted on the x-axis in FIG. 5 and inFIGS. 6 to 8. The representations inFIGS. 5 to 8 are to be viewed as schematic, and the time intervalsrepresent an approximate duration of the processing time of thesemiconductor substrates at the workstations. In the exemplaryembodiment illustrated in FIG. 5, three semiconductor substrates 6 arelocated simultaneously in the arrangement 3. A visual macro inspectionis not carried out by the operator in this exemplary embodiment. At thebeginning of the flow of the semiconductor substrates 6 in thearrangement, the first semiconductor substrate 6 ₁ is at the transferposition 8 a, the second semiconductor substrate 6 ₂ is in the macroinspection 10 a, and the third semiconductor substrate 6 ₃ is in themicro inspection 12 a. The transfer position 8 a, the macro inspection10 a and the micro inspection 12 a are illustrated as a dashed line inFIGS. 5 to 8. The residence time of the semiconductor substrates isidentified by vertical lines in FIGS. 5 to 8, and the interspace isdesignated by the reference symbol of the semiconductor substrate justbeing processed.The changer 14 makes a stroke in the axial direction (in each caserepresented by an upward arrow in FIGS. 5 to 8) and lifts the second andthe third semiconductor substrates 6 ₂ and 6 ₃ off the macro inspection10 a and the micro inspection 12 a, respectively. The changer 14rotates, and in this way the first semiconductor substrate 6 ₁ reachesthe macro inspection 10 a, the second semiconductor substrate 6 ₂reaches the micro inspection 12 a and the third semiconductor substrate6 ₃ is finally transported to the transfer position 8 a and transferredto the substrate feed module 1. The changer 14 is then lowered (in eachcase represented by a downward arrow in FIGS. 5 to 8) and rotated backthrough −120° with empty arms. A fourth semiconductor substrate 6 ₄ isfed to the empty arm at the transfer position 8 a from the substratefeed module 1. Before this exchange is carried out, the necessaryinspection has been carried out on the first and second semiconductorsubstrates 6 ₁ and 6 ₂ at the second and third workstations 10 and 12.After a certain time, the changer 14 again carries out an axial stroke,in order to initiate the cycle n+1. The changer 14 once again makes anaxial stroke and carries out a rotation by +120°. The fourthsemiconductor substrate 6 ₄ therefore reaches the macro inspection 10 a,and the first semiconductor substrate 6 ₁ is fed to the micro inspection12 a. The movement sequence of the changer 14 is identical to thatalready mentioned above. At the transfer position 8 a, the secondsemiconductor substrate 6 ₂ is replaced by a fifth semiconductorsubstrate 6 ₅. This fifth semiconductor substrate 6 ₅ then passesthrough the workstations 8, 10 and 12 in the arrangement 3 in thefollowing cycle.A further embodiment of the handling of the semiconductor substrates 6in the arrangement 3 is disclosed in FIG. 6. In this case, a macroinspection is additionally carried out by the user. Just as at the startof the flow of semiconductor substrates 6 disclosed in FIG. 5 in thearrangement 3, the first semiconductor substrate 6 ₁ is at the transferposition 8 a, the second semiconductor substrate 6 ₂ is in the macroinspection 10 a and the third semiconductor substrate 6 ₃ is in themicro inspection 12 a. The changer 14 makes an axial stroke and liftsthe second and the third semiconductor substrates 6 ₂ and 6 ₃ off themacro inspection 10 a and the micro inspection 12 a, respectively. Thechanger 14 rotates through +120° and, in this way, the firstsemiconductor substrate 6 ₁ reaches the macro inspection 10 a, thesecond semiconductor substrate 6 ₂ reaches the micro inspection 12 a andthe third semiconductor substrate 6 ₃ is finally transported to thetransfer position 8 a and transferred to the substrate feed module 1.While the micro inspection 12 a is being carried out at the thirdworkstation 12, the changer 14 is lowered axially and is then rotatedthrough −60°. The changer 14 is thus moved out of the working range ofthe second workstation 10. This is necessary, since the semiconductorsubstrate 6 in the second workstation 10 is pivoted in the visual rangeof the operator and rotated, in order to detect possible macroscopicfaults on the semiconductor substrate 6. When the visual macroinspection has been completed, the changer 14, which is still lowered,rotates through a further −60°. A fourth semiconductor substrate 6 ₄ isfed to the arm at the transfer position 8 a from the substrate feedmodule 1. Before this exchange was carried out, the necessary inspectionhas been carried out on the first and second semiconductor substrates 6₁ and 6 ₂ at the second and third workstations 10 and 12. After acertain time, the changer 14 again carries out an axial stroke, in orderto initiate the cycle n+1. The changer 14 once more makes an axialstroke and a rotation through +120°. The fourth semiconductor substrate6 ₄ thus reaches the macro inspection, and the first semiconductorsubstrate 6 ₁ is fed to the micro inspection 12 a. The movement sequenceof the changer 14 is identical to that already mentioned above. At thetransfer position 8 a, the second semiconductor substrate 6 ₂ isreplaced by a fifth semiconductor substrate 6 ₅. This fifthsemiconductor 6 ₅ then passes through the workstations 8, 10 and 12 inthe arrangement 3 in the following cycle.FIG. 7 shows a representation of a cycle in which a poor semiconductorsubstrate has been found during the visual macro inspection. Here, justas already shown in FIG. 6, a visual macro inspection is carried out bythe user. Just as at the start of the flow of semiconductor substrates 6disclosed in FIG. 5 in the arrangement 3, the first semiconductorsubstrate 6 ₁ is at the transfer position 8 a, the second semiconductorsubstrate 6 ₂ is in the macro inspection 10 a and the thirdsemiconductor substrate 6 ₃ is in the micro inspection 12 a. The changer14 makes an axial stroke and lifts the second and the thirdsemiconductor substrates 6 ₂ and 6 ₃ off the macro inspection 10 a andthe micro inspection 12 a. The changer 14 rotates through +120° and, inthis way, the first semiconductor substrate 6 ₁ reaches the macroinspection 10 a, the second semiconductor substrate 6 ₂ reaches themicro inspection 12 a, and the third semiconductor substrate 6 ₃ isfinally transported to the transfer position 8 a and transferred to thesubstrate feed module 1, the changer 14 being lowered axially. While themicro inspection 12 a is being carried out at the third workstation 12,changer 14 is then rotated through −60°. Thus, as already mentioned inFIG. 6, the changer 14 is moved out of the working range of the secondworkstation 10. During the visual macro inspection, the firstsemiconductor substrate 6 ₁ has been identified as faulty. A fourthsemiconductor substrate 6 ₄ which may possibly already have beentransferred to the changer 14 at the transfer position 8 a, istransported back into the substrate feed module 1 again. The changer 14,lowered axially, rotates through a further +60°. One arm of the changer14 accepts the first semiconductor substrate 6 ₁ by lowering the secondworkstation 10 into the basic position. It is necessary to lower theworkstation 10 into the basic position in order that the changer 14 canrotate freely. The changer 14 rotates through −120° in the lowered stateand thus brings the first semiconductor substrate 6 ₁ into the transferposition 8 a. The second semiconductor substrate 6 ₂ is still in thethird workstation 12 or the micro inspection 12 a. At the transferposition 8 a, the first faulty semiconductor substrate 6 ₁ istransferred to the substrate feed module 1, and a fourth semiconductorsubstrate 6 ₄ from the substrate feed module 1 is deposited on thechanger 14. Finally, the changer, lowered, rotates through +120° andbrings the fourth semiconductor substrate 6 ₄ to the second workstation10. The fifth semiconductor substrate 6 ₅ is transferred to the changer14 at the transfer position 8 a. The changer 14, lowered, then rotatesthrough −60°, in order to leave the active range of the secondworkstation 10 free. At the first workstation 10, the visual macroinspection is carried out on the fourth semiconductor substrate 6 ₄.After the visual macro inspection has been completed, the changer 14again rotates through −60° and then the semiconductor substrates locatedin the arrangement 3 can be changed in accordance with the methodalready described in FIG. 5 and FIG. 6.FIG. 8 shows an embodiment of the method for handling semiconductorsubstrates in which only one semiconductor substrate 6 per cycle isexamined in the arrangement 3. No visual macro inspection takes place.The first semiconductor substrate 6 ₁ is transferred from the substratefeed module 1 to the changer 14. The changer rotates through +120° andthe first semiconductor substrate 6 ₁ is transferred to the secondworkstation 10. There, the alignment of the first semiconductorsubstrate 6 ₁ is determined and the identification 30 on the firstsemiconductor substrate 6 ₁ is then read. In the meantime, the changer14, lowered axially, rotates through −120°. The changer then makes a zstroke and removes the first semiconductor substrate 6 ₁ from the secondworkstation 10. The changer rotates through +120° and transfers thefirst semiconductor substrate 6 ₁ to the third workstation 12, where themicro inspection is carried out. After the micro inspection, the changer14 makes an other z stroke, removes the first semiconductor substrate 6₁ from the third workstation 12 and rotates through −120°. The firstsemiconductor substrate 6 ₁ in turn passes to the second workstation 10and, there, the notch 32 is determined, so that the first semiconductorsubstrate 6 ₁ is aligned. In the meantime, the changer 14, loweredaxially, rotates through +120°. The changer 14 then makes an axialstroke, removes the first semiconductor substrate 6 ₁ from the secondworkstation 10 and rotates through −120°. The first semiconductorsubstrate 6 ₁ is then at the transfer position 8 a and is transferred tothe substrate feed module 1. A second semiconductor substrate 6 ₂ isremoved from the substrate feed module 1 and, using the secondsemiconductor substrate 6 ₂, the method already described above iscarried out as for the first semiconductor substrate 6 ₁.It is self-evident that, depending on the number of semiconductorsubstrates 6 in the arrangement 3, or changes in the flow of thesemiconductor substrates 6 through the arrangement 3, such as theremoval of defective semiconductor substrates 6, the residence time ofthe semiconductor substrates at the individual workstations 6 maychange. Consequently, this also has an effect on the cycle time.The invention has been described with reference to a special embodiment.However, it is self-evident that changes and modifications can becarried out without leaving the scope of protection of the followingclaims in so doing.

1. Method for transporting and inspecting semiconductor substrates,comprising the steps of: providing at least three workstations and achanger arranged in a housing, the workstations and the changer allbeing open to each other in such a way that each of the workstations canbe supplied with a semiconductor substrate; lifting the changer andcarrying out a rotational movement by a specific angular amount, inorder to transfer at least one of the semiconductor substrates toanother workstation; lowering the changer and carrying out a rotationalmovement by the same angular amount in the opposite direction, without asemiconductor substrate resting on the changer; and picking up a newsemiconductor substrate from a substrate feed module.
 2. Methodaccording to claim 1, wherein the first workstation defines a transferposition, at which the semiconductor substrates are transferred from asubstrate feed module into the housing or are transported back from thehousing into the substrate feed module.
 3. An arrangement fortransporting and inspecting semiconductor substrates, comprising: atleast three workstations arranged in a housing; and a changer arrangedin the same housing and at least three workstations being open to eachother such that each of said workstations can be supplied with asemiconductor substrate; said changer being rotatable by a specificangular amount in order to transfer at least one of the semiconductorsubstrates from one of said workstations to another of saidworkstations; said changer being further rotatable by said specificangular amount in an opposite direction without transporting asemiconductor substrate in order to pick up a new semiconductorsubstrate from a substrate feed module.